Autoimmune Hypothyroiditis in Dogs

Autoimmune Hypothyroiditis in Dogs

Health & Safety

Autoimmune Hypothyroiditis is one of the commonest thyroid health issues seen in dogs. It occurs when the antibodies found in the blood or in tissue begin attacking a dog's thyroid gland and this can seriously and negatively impact the amount of two essential hormones being produced. The hormones are T3 and T4 which are triiodothyronine and thyroxine respectively.

T3 and T4 are needed in many of the body's functions and as such a deficiency in either or both will have an adverse on their functions and this includes the function of a dog’s thyroid gland. It is not known why the antibodies start to attack, but it is thought there is a genetic connection in certain breeds. A lot of research has been carried out into why Samoyeds are so affected by the condition. With this said, some studies have shown that around fifty other breeds could also suffer from Autoimmune Hypothyroiditis.

Signs to Watch Out For

Unfortunately, any outward signs of there being a problem are usually missed because it is not until a good percentage of the Thyroid gland has been attacked and destroyed by a dog's antibodies that any clinical signs start to show themselves. However, dogs typically begin to develop the condition when they are anything from 2 to 5 years old.

The Thyroid is one of the most important glands in the body and if it is damaged in any way, it can negatively impact many other organs in a dog's body. Signs there may be a problem include the following:

  • Dogs develop alopecia
  • There's a greasy regrowth of hair on their bodies and tails
  • Lethary
  • Weight gain/obesity
  • A reluctance to do any exercise
  • Thinning of the skin
  • Black skin pigmentation
  • Dandruff
  • Intolerance of cold
  • Lipidosis - fat deposits in the cornea
  • Keratitis sicca – dry eye
  • Diarrhoea
  • Nausea
  • Constipation
  • Bradycardia – slow heart rate
  • Muscle weakness
  • On top of the above, a dog suffering from the condition may also show some quite serious neurological symptoms which includes the following:
  • Ataxia
  • Turning in circles
  • Aggression
  • Infertility in both male and female dogs


Research has shown that a several genes could be responsible for certain breeds to be more predisposed to inheriting the disorder although there is some suggestion that toxins and nutrition could also play an important role in triggering the condition in breeds that are known to suffer from the condition too.

Diagnosing the Problem

A vet would need to see a dog's full medical history before carrying out a thorough physical examination which would entail carrying out blood tests. Today, there are several blood tests for both AH and hypothyroidism thanks to the advancement in veterinary medicine. The levels of both T3 and the T4 hormones can be established although the first tests would only determine how well a dog's thyroid gland is functioning rather than establish if they are suffering from Autoimmun Hypothyroiditis. To determine this a vet would recommend carrying out a TgAA test.

It can prove challenging when interpreting the results of these tests and as such vets would typically recommend that a vet who has experience in Endocrinoloy carry out the work to establish a correct diagnosis because it’s essential that other causes need to be accounted for which could well affect the results of a thyroid test coming up as being abnormal. This includes certain medications a dog may have been previously prescribed by a vet to treat another condition.


Vets have various options at their disposal when it comes to drugs they can use to treat a dog when they have been diagnosed as suffering from Autoimmune Hypothyroiditis. A dog would need to be given their medication daily and have checkups every fortnight to make sure the dosage is correct which a vet would establish by taking further blood tests. Overweight or obese dogs suffering from the condition would generally start to shed the excess pounds once they start taking the medication, but their weight loss needs to be closely monitored to make sure dosages are correct.

Living and Management

Dogs suffering from the condition need to be carefully monitored for the rest of their lives and this includes having regular health checks at the vets. They would also need to have regular blood tests to make sure their thyroid glands are producing enough T3 and T4 hormones and to ensure that the dosages of any medications they are taking are correct bearing in mind that these often need to be increased or decreased depending on the results of blood tests.

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